1. Field of the Invention
The present invention is directed to a V-belt used in particular, for continuous speed variators, and, still more specifically, to a V-belt made of a viscoelastomeric material, comprising two groups of teeth disposed on the upper and lower portions respectively, of the belt.
2. Background of the Prior Art
As is known, in many of the applications of these belts, the V-belts transmit horsepower when contacting the flanks of the trapezoidal groove of the pulleys, which are characterized by having a very small winding diameter, for example, of 70 mm or even less.
These belts must be able to adapt to said small bending radii of the pulleys without sustaining any ruptures or any slits appearing in the elastomeric material wherein various reinforcing elements are embedded therein.
For attaining the cited aim, there has already been provided to make a special toothing in the lower portion of the belt in such a manner as to allow for the belt to have a good degree of longitudinal flexibility during its winding over the pulleys. Unfortunately, the formation of the teeth in the belt body can lead to their buckling under peak loads as a result of combined high compression and bending loads, transmitted by the pulley flanks in transmitting motion. Hence, there exists a limit to the service life of the presently known V-belts and particularly, in the field of continuous transmission for speed variators, where the horsepower to be transmitted is quite high, and the corresponding thrusts can exceed, for example, a load of 200 Kg on four or five teeth when contacting the flanks of the grooved pulley.
For resolving the above-cited drawback, one can contemplate stiffening of the belt, for example, by having recourse to transverse struts that terminate at the sides with an inclination corresponding to that of the opposite flanks, in a grooved pulley. In this case, in being directly in contact with the pulley flanks, said struts could allow for a certain increase in the horsepower as compared with the previously cited belts.
However, as is understandable, said struts constitute elements that can alter both the construction as well as the function of the elastomeric V-belts, i.e. since it is no longer the elastomeric part of the belt flanks that receives and transmits horsepower upon coming into contact with the pulley but rather the above-noted struts. Often these struts are cumbersome, too robust, too difficult to be applied and, in particular, are excessively heavy and therefore, under the working conditions of a belt when it is transmitting motion at high speeds, the struts can cause intolerable stresses on the belt body owing to the effect of the centrifugal force.